The present invention relates to catalytic gas generators for producing high-temperature gases from a liquid, particularly generators used in monopropellant rocket engines and other power generating applications, and most particularly to an improvement relating to catalyst beds employed in such gas generators.
Small rocket engines of the type utilized in space satellites are generally of monopropellant design employing a catalytic gas generator to convert a liquid propellant such as hydrazine into a high-temperature gas. Such engines incorporate a catalyst bed within their thrust chambers. The propellant is injected into the catalyst bed where it reacts to produce a high-temperature gas. The gas exits from the catalyst bed and is expanded through a conventional nozzle system to produce thrust. The primary life-limiting component of such monopropellant rocket engines is the catalyst used for decomposing the propellant into a high-temperature gas. Catalyst attrition resulting from loosening of the catalyst bed due to differential thermal expansion and contraction ultimately creates voids in the catalyst bed causing both a reduction in efficiency and ultimate destruction of the catalyst bed so that it is incapable of performing its intended function. Such catalyst attrition has been indentified as one of the major causes limiting the life capability of catalytic gas generators and thus the rocket engines in which they are utilized.
Prior attempts at reducing the deleterious effect of void formation in catalytic gas generators, although providing some improvement, have not adequately solved the problem so that the life of such a rocket engine can reliably exceed 10.sup.6 pulses. For example, prior attempts to dynamically retain the catalyst bed, that is, to dynamically change the bed boundaries as voids occur by employing axially movable boundary plates, have met with limited success because, among other reasons, the dynamic retention devices have been exposed directly to the relatively hot decomposition gases of the propellant.
It is an object of the present invention to provide a catalyst bed for use in a catalytic gas generator, for example, of the type used in a monopropellant rocket engine, that has a long life, and preferably a catalyst bed that can reliably achieve up to and exceed 10.sup.6 impulses. It is a further object of the present invention to provide a catalyst bed retention device, and more particularly, a dynamic retention device that is not susceptible to the problems encountered with prior art devices.